The objective of the proposed research is to synthesize a number of polycholorinated biphenly (PCB) arene oxides and study their chemical reactively. The compounds studied will include one or more of the possible isomeric arene oxides which have been shown or are thought to be intermediates in the metabolism of the following PCB's: 2,4,2',4'-2,5,2',5'- and 3,4,3',4'-tetrachloro-; 4,4'-dichloro-; 2,4,5,2',4',5'-hexachloro. In addition to the previous successful approaches we have used to prepare the 3,4-epoxide of 2,5,2',5'-tetrachlorobiphenyl and the 1,6- and 5,6-epoxides of 3,4,3',4'-tetrachlorobiphenyl, the present work will employ Diels-Alder reactions between several chlorinated (and/or silylated) butadienes and 2-aryl-3-sulfinyl-acrylate esters to prepare suitably functionalized precursors to the benzene oxide ring. The cholorinated biphenyl oxides prepared will be compared as to their ease and pH dependence of aromatization and their reactivity towards thiol nucleophiles. Attempts will be made to assess reactivity as a function of epoxide position relative to the aromatic phenyl substituent, (including compounds have chlorine on the epoxidized carbon) and according to the number and position of the chlorine substituents on both the aromatic and benzene oxide rings. Several polybrominated biphenyl (PBB) arene oxides will also be prepared and compared with their chlorinated analogs.